Lymph nodes are small, kidney-shaped organs found throughout the body. Full of immune cells, the lymph nodes’ function is to clear out foreign objects and support the immune system. Lymph nodes communicate with the tissues and with each other through the lymphatic vessels, which carry fluids and objects from the tissues and back out to the bloodstream. Normally, lymphatic vessels grow during the embryo stage, but also in adults during wound healing, cancer, and inflammation. But the exact mechanism of this "lymphangiogenesis" is yet unknown. Ecole Polytechnique Fédérale de Lausanne (EPFL) scientists have now identified the molecules that signal the growth of lymphatic vessels during worm infections. The work was published on August 28, 2017 in Nature Communications. The open-access article is titled “Interactions Between Fibroblastic Reticular Cells and B Cells Promote Mesenteric Lymph Node Lymphangiogenesis.” The lymphatic vessels drain pathogens from tissues to the collecting lymph nodes, where immune responses begin. These vessels also allow lymphocytes and dendritic cells --which expose pathogen material to trigger the immune system -- to flow in and out of the lymph nodes. Because of this, lymphangiogenesis is important for immune responses against infections. But recent studies have shown that lymphangiogenesis can also regulate immune responses during inflammation. This connection between inflammation and lymphangiogenesis is key in our understanding of the adaptive immune response, which is the slower but more specialized wave against infections and involves T and B cells. The lab of Dr. Nicola Harris at EPFL looked at the mesenteric lymph node, which collects fluids and material from the intestine of mice. The research, led by Dr. Lalit Kumar Dubey, follows a 2016 paper from the group, which showed how worm infection stimulates B cells to “talk” to the endothelial cells of the mesenteric lymph node and kick-start an immune response.
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